The correct answer is C. Interference.
When white light hits a soap bubble, the light waves are reflected off the front and back surfaces of the bubble. The reflected waves interfere with each other, creating an interference pattern. The interference pattern is what causes the soap bubble to appear colored.
The colors that are produced by the interference pattern depend on the thickness of the soap bubble. The thicker the bubble, the more colors will be produced. The colors are also affected by the angle at which the light hits the bubble.
Diffraction is the bending of light as it passes through a narrow opening or around an obstacle. Polarization is the separation of light into two waves that vibrate in perpendicular directions. Reflection is the bouncing of light off a surface.
I hope this helps!